A New Take on the Classic Pass Labs D1 with an ESS Dac - Page 87 - diyAudio
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Old 27th January 2012, 09:04 PM   #861
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Something you didn't see is two full racks of test cables, test probes, scope probes that I got for free! I took them from the garbage dumpster once they close the shop. Also they were throwing away a very nice custom made bench (see the green door one). Got this one for free, including wood storage boxes that fit inside the lower section to neatly class spare parts.
The scavenger was there, me

I have also the usual assortment of parts bins, parts shelves, etc...So it is my own cavern in the basement, with test sound system.
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File Type: jpg Lab 003.jpg (170.1 KB, 425 views)
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Old 27th January 2012, 09:10 PM   #862
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I have three shops really in my home (and an understanding wife). My electronic room that you just saw, the usual garage for the metal, drilling, cutting works and a smaller corner I made for myself in the ventilation room where I make my pcb, equipped with exposition table, dremel and even a big sink for the developer, etc. I do the etching in the garage because of the full smells of the etching solution.

I'll do my own D1 prototype PCB there over the weekend.
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Old 27th January 2012, 09:17 PM   #863
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One question I had is that in your instructions you said to adjust 24V on R1 (Id 120ma), but then you're saying 21V, and indicating 21V on your schematic. 21V is not 120ma Id. What is the correct voltage 24 or 21V? Thanks...
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Old 28th January 2012, 02:23 AM   #864
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This is my preliminary results. Two matched pairs already. Do these numbers making sense?
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Old 28th January 2012, 03:58 AM   #865
opc is offline opc  Canada
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Hi Algar,

You're definitely getting good results if your transconductance numbers are between 0.8 and 1. If you have a large enough batch, you should be able to find two tightly matched pairs that are in the upper 0.9 region. Those are the ones you want!

Keep good track of all your numbers as I'm sure there are people here who would be interested in matched pairs if you have extras.

If you want to do a consistency check, re-measure one of the earlier ones and see if you get roughly the same number.

Keep up the good work, and kudos on the very nice test bench!

Cheers,
Owen
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Old 28th January 2012, 04:27 AM   #866
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Thanks for the confirmation. I should have completed the batch this weekend. I let them stabilize for about 15 min. while watching TV.
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Old 28th January 2012, 05:37 AM   #867
qusp is offline qusp  Australia
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Quote:
Originally Posted by Algar_emi View Post
One question I had is that in your instructions you said to adjust 24V on R1 (Id 120ma), but then you're saying 21V, and indicating 21V on your schematic. 21V is not 120ma Id. What is the correct voltage 24 or 21V? Thanks...
i assume this question is for Owen yes? yeah i had this same confusion at first. its definitely 24. check the scheme i posted, it has the voltages noted on it as well. i think opc wrote down a Freudian slip and wrote VDS, which is generally about 21 when the voltage across R1 is 24

yeah you tend to get a group that are similar then a jump. those numbers look right, but they are pretty low for these fets. i discarded anything below 0.9s or rather i still have them, but i didnt have them in the pool for matched sets.

Last edited by qusp; 28th January 2012 at 05:45 AM.
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Old 28th January 2012, 08:21 PM   #868
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Here the final match results. I know my AC results are much lower than yours. It may be my setup. I'll recheck them into the actual circuit.
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Last edited by Algar_emi; 28th January 2012 at 08:26 PM.
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Old 28th January 2012, 08:25 PM   #869
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Here my proto PCB. I guest I won't need to group buy.
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Old 28th January 2012, 08:30 PM   #870
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I removed my own order.

1. cersepn x 1
2. icewall x 2
3. pmchoong x 1
4. qusp x 1 this is tentative mate, but wanted to make sure my name was down
5. regal
6. randytsuch x 1
7. LK x1
8. greyrab x1
9. alexcount x1
10. adelias x1
11. Coolhead x1
12. Emphrygian x 1
13. tranhieu x 1
14. crazyfrog x 1
15. woresseo x 2
16. Pedefede x 1
17. ggetzoff x 1
18. syklab x1 + fets
19. Magsy x 1
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